miami building collapse

Why Did the Surfside Condo Tower Collapse? Here Are All the Theories.

“Buildings in America do not just fall down like this.” Photo: Chandan Khanna/AFP via Getty Images

After a huge segment of the 12-story Champlain Towers South condominiums collapsed, the building’s still-standing wing served as a reminder of the devastating loss of life, its grid of ragged interiors occupied just moments before by sleeping residents. At least 118 of those residents are still missing, and 27 people are confirmed dead. Such a rare catastrophic event demands immediate answers: How can a 136-unit building in an affluent area near Miami Beach, one that’s only about 40 years old, crumble into rubble? “Buildings in America do not just fall down like this,” said Surfside’s Mayor Charles Burkett at a news conference. “There is a reason. We need to find out what that reason is.” But the factors — and there likely will be multiple factors — that caused the collapse of Champlain Towers South may not be fully revealed for weeks.

The sheer incongruity of a building suddenly collapsing — particularly a newish coastal building engineered to handle extreme-weather conditions including hurricane-force winds — evokes an act-of-God-level explanation. And whether or not this particular disaster can be attributed specifically to climate change, our greatest existential threat, it should mark the beginning of a reckoning about why, as a country, we continue to invest so heavily in construction to reside in places that have been deemed high risk, says Ann Tihansky, physical scientist with the U.S. Geological Survey. “This is the geologist perspective, because we’re always looking long term,” she says. “I think there’s a talking point here about infrastructure and making smart investments for the future, using the best available science to make decisions, and not putting ourselves in harm’s way.”

Rising seas seems like an exceedingly obvious scapegoat, particularly in a state where leaders have largely attempted to ignore the climate crisis. As reports trickle out that warnings by local building inspectors went unheeded, there are growing calls for investigations into potential malfeasance. And, of course, there are conspiracy theorists reviewing slow-motion security footage that, they claim without evidence, shows signs of a detonation. What’s more likely, suggests Guy Nordenson, a New York–based structural engineer, is not a single reason but rather several conditions that added up to structural failure. “There’s usually a whole number of things that cascade: You have corrosion, you have potential subsidence,” he says. “Inevitably, there are going to be a number of causes that will be found to have combined.” With the standing segment of the structure collapsed by controlled demolition on July 4 to aid rescue efforts, experts will be able to access more of the site, and we’ll update this post as further evidence comes in.

Theory No. 1: Cracks in Structural Columns

According to a 2018 report, a consultant hired by the building’s condo board uncovered cracks, breaks, and crumbling in the structural concrete, a phenomenon known as spalling. In April 2021, an urgent letter from the condo board’s president warned that “concrete deterioration is accelerating” and noted that estimates for repairs had increased to $16 million, set to begin this summer. Some of the most worrisome damage had been found in the subterranean parking garage, which just last week had water leaking from the pool deck. The pool deck is also where a resident in a fourth-floor apartment witnessed a hole opening just before the building collapsed. Spalling was so pronounced in some parts of the building that it can be easily seen in recent Google street-view images, and although damage to balconies and exterior walls would not necessarily threaten the integrity of the building, it could be a sign of real rot within. If there was a column failure in the parking garage, that might explain the way the building slumped downward in what’s called a progressive collapse. A July 2 Miami Herald report which features a video taken by a tourist moments before the structure fell isolates the initiation point as a collapsed slab in the parking garage that pulled away from a column, known as punching shear failure.

Theory No. 2: Vibrations From Construction Next Door

Across the street — but located in the adjacent city of Miami Beach — is Eighty Seven Park, a new 18-story, 71-unit luxury tower designed by Renzo Piano and developed by Terra, which opened last year. During construction, residents in Champlain Towers complained about shaking and vibrations, with one condo-board member writing to Surfside officials in January 2019 that workers were “digging too close to our property and we have concerns regarding the structure of our building.” The Surfside official replied at the time that the city had no jurisdiction to stop the construction and advised the condo board to hire an outside consultant to monitor any concerns. While construction work can compromise nearby buildings — for example, an empty Murray Hill building collapsed last summer while workers were excavating the adjacent construction site — it would be less likely to happen here, says Nordenson, where new buildings are specifically engineered to withstand the vibrations created by the direct hit of a strong hurricane.

Theory No. 3: Barrier Island Erosion

Surfside, like much of the populated corridor of South Florida, is located on a barrier island, a shifting berm of sand that serves as a frontline coastal defense, absorbing the impact of storm surges and hurricanes. Millions of Americans also live on barrier islands, even though they’re vulnerable to being reshaped or even washed away entirely over time. Erosion may not have caused the collapse, but it is a reason for the building to not be located there at all, says Albert Hine, a geological oceanographer who taught for many years at the University of South Florida. “In 100 years, at high tide, most streets in Miami will be flooded — is that habitable? In the short term, there will be more hurricanes and more extreme-weather events,” he says. “Maybe we’d better not build any more high-rises here. The long-term goal is ultimately abandonment.”

Theory No. 4: Subsidence Exacerbated by Sea-level Rise

According to a 2020 report, the ground under Surfside, like many parts of Florida, is sinking. Buildings can shift, but Champlain Towers was singled out in the report owing to its relatively higher rate of subsidence, a rate of 2 millimeters per year. The tower was built on piles, says Nordenson, meaning if even one was not properly anchored, the structure could be impacted by settling or soil incongruities, which might cause additional geotechnical issues. The question this raises in Hine’s mind is whether subsidence was resulting from the potential use of fill when the buildable land of the island was expanded and whether the piles were actually anchored in bedrock. “But if there’s widespread subsidence, there’d be cracked and falling concrete on every building along there, and I haven’t seen that.”

Theory No. 5: Shoddy Construction Practices During the 1980s Building Boom

One theory seemed extremely plausible to both Nordenson and Hine: a major structural flaw. The July 2 Herald report points to fewer-than-normal shear walls which might have provided necessary redundancy if a slab failed. A forensic engineer told the New York Times that fewer steel reinforcements were observed in the collapsed columns than were called for in the building’s original plans. The Miami Herald’s editorial board published a scathing opinion piece noting that Champlain Towers was built during a time when buildings went up fast, cheap, and underregulated, thanks, in part, to the nationwide savings-and-loan scandal. “We know that building codes for single-family homes during that era were weak, and enforcement was lax, something that became terribly apparent when Hurricane Andrew roared through southern Miami-Dade County,” the opinion piece reads. “So when we look at the images of the destruction in Surfside, we’d be fools not to wonder whether slipshod construction and look-the-other-way enforcement of that era played a part.” Two nearby condo buildings — the 10-story Crestview Towers in North Miami Beach and a three-story building on Lenox Avenue in Miami Beach — were evacuated this week after inspections found similar damage.

Theory No. 6: Sinkhole

The geology of Florida — which sits on dissolvable limestone where cavities can form and subsequently collapse — makes it the sinkhole capital of the U.S. Large sinkholes have opened up elsewhere in the state, swallowing cars, roadways, and, in a few cases, entire buildings. But even smaller sinkholes can cause more minor structural issues over time. Miami-Dade County’s Mayor Daniella Levine Cava — who has ordered all local buildings at least 40 years old to be reinspected within 30 days — said Monday there’s no evidence that a sinkhole is responsible. That’s probably accurate, says Hine — the building’s specific location isn’t a likely spot for sinkholes.

Theory No. 7: Seawater Weakened Structural Rebar

If the spalling had compromised structural columns, it’s possible that saltwater intrusion — which has increased in recent years owing to sea-level rise — might have seeped into the columns, rusting and weakening the steel rebar that strengthens the concrete. It was something the former building manager had expressed concern about 30 years ago, noting that he witnessed “a lot of saltwater come in through the bottom of the foundation … so much water, all the time, that the pumps never could keep up with it.” Engineers quoted in a Washington Post report note that because the slab above the pool joined an exterior wall, heavy corrosion due to water damage may have been enough to pull the structure down. While coastal buildings are, hypothetically, engineered to withstand exposure to the corrosive effects of saltwater, conditions have changed enough in the 40 years since the building was constructed that it’s worth considering new theories for the ways structures might be compromised, says Nordenson. “Climate change is putting a lot of stress on our buildings and our infrastructure, from heat to flooding,” he says. “The initial information seems to point in the general direction toward challenging our assumptions of how durable buildings are. We have to think about how quickly things might deteriorate under these particular circumstances.”

All the Theories About the Surfside Condo Tower Collapse